Twin-shaft turbine engines comprise a high-pressure turbine arranged at the output of a combustion chamber to remove energy from a primary gas flow discharged by said combustion chamber and drive a high-pressure compressor positioned upstream of the combustion chamber and supplying said chamber with pressurized air. These turbine engines also comprise a low-pressure turbine arranged downstream of the high-pressure turbine to remove excess energy from the primary gas flow and rotate a low-pressure compressor arranged upstream of the high-pressure compressor.
The high-pressure compressor of these turbine engines can include a centrifugal downstream stage comprising an impeller.
Their high-pressure turbine generally comprises a distributor formed by a plurality of static vanes positioned at the output of the combustion chamber, and a vaned disk mounted downstream of the distributor and rotated by the flow of gases discharged by the combustion chamber.
The vaned disk of the high-pressure turbine and the impeller of the high-pressure compressor are connected to one another and are part of a high-pressure rotor of the turbine engine, so that the disk of the turbine can rotate the impeller of the compressor, in a well-known manner.
The downstream surface of the impeller of the high-pressure compressor is generally cooled by an air flow sampled at the output of said compressor, and the flow rate of which is adjusted by the play between the rotary part and the static part of a labyrinth seal, which separates a first annular cavity delimited in particular by the downstream surface of the impeller, from a second annular cavity in which a cooling air flow for cooling the vanes of the disk of the high-pressure turbine circulates as well as an air flow intended to supply a bleed cavity to limit the leakage risks at the primary flow between the distributor and the vaned disk of the high-pressure turbine.
However, in some of these turbine engines, the flow rate of the cooling air flow of the impeller can be higher than what is necessary to ensure said cooling.
This can in particular result from excessive play between the rotary portion and the static portion of the aforementioned labyrinth seal, which can in particular occur during a change in the operating rating of the turbine engine.
Part of the flow delivered by the high-pressure compressor is then pointlessly sampled on the primary flow, which considerably reduces the performance of those turbine engines.
Furthermore, the cooling air flow of the impeller is hotter, when it reaches the second annular cavity, than the cooling air flow of the vanes of the disk of the high-pressure turbine. The mixture of the two aforementioned flows therefore causes a harmful increase in the temperature of the cooling air flow of the vanes, and even more so as the flow rate of the cooling air flow of the impeller is higher.